1. Field of The Invention
The present invention relates to a socket for an electrical part for detachably holding an electrical part such as semiconductor device (called “IC package” hereinlater).
2. Related Art of the Invention
In a known art, there has been provided an IC socket, as “socket for an electrical part” of a kind mentioned above, for accommodating an IC package as “electrical part”.
In such IC package, a number of solder balls as “terminals” are provided so as to project from a lower surface of the IC package and these solder balls are arranged in lattice having vertical and horizontal rows.
On the other hand, the IC socket has a socket body into which the IC package is accommodated and to which a number of contact pins contacting the terminals of the IC package are arranged. The socket body is also provided with a movable member, which is urged upward to be vertically movable by means of coil spring, for elastically deforming the contact pins so as to be contacted to or separated from the terminals of the IC package, respectively.
Furthermore, a lever member for vertically moving this movable member is attached to the socket body to be pivotal or rotatable about a rotational shaft and an operation member for rotating this lever member is also mounted to the socket body to be vertically movable.
Through the vertical movement of the operation member, the lever member is rotated and the movable member is then moved vertically. Accordingly, the contact pins are elastically deformed and contact portions of the contact pins are contacted to or separated from the terminals of the IC package.
However, In such conventional structure, the lever member is made of metal material, the movable member is made of synthetic resin, and the lever member has a pressing (pushing or depressing) portion which presses the movable member and provides an R-shape, and on the contrary, the movable member has a portion to be pressed (pushed or depressed) by the pressing portion of the lever member, which provides a flat surface shape. Therefore, the pressing portion of the lever member is always linearly contacted (i.e., achieves a line contact) to the movable member.
Because of the above reason, as the lever member is rotated so as to move the movable member downward, a stress directing upward acting to the movable member is increased by a reaction force of the coil spring which urges the movable member upward, and this stress becomes maximum at a time when the movable member is pressed downward to the most downward position (lowest position of the movable member). If an IC socket having such structure is used repeatedly, the pressed portion of the movable member made of synthetic resin will be worn or broken because the movable member is made of synthetic resin where as the lever member is made of metal material. The wearing or breaking of the pressed portion of the movable member will result in the reduction of the lowering amount of the movable member and, hence, an opening degree of the contact portion of the contact pin cannot be ensured to an amount capable of receiving the solder ball in the contacting/separating manner.